Here in my office I use a Leica Hektor 1:2,5/85mm slide projector lens (3$ flea market ;-) ).zzffnn wrote:Thank you! So what visual magnification does that lens provide? Sorry, my optical math is terrible. That particular Leica lens seems to sell for over $50 USD and slightly out of my budget for this application though.lothman wrote:go for a slide projector lens, for example a Leica colorplan 90mm. Will give you more than a 4x loupe but has excellent sharpness even to the extreme corners, best color, no distortion, good working distance and a robust housing.
If I use it direct near my eye (similar a watchmakers loupe) I have a field of view of ø5cm, if I use it at distance held by hand I get a FOV of ø1,5cm kind of vignetting. But I can move my head and look around in the lens in my hand and the can see the same 5cm FOV.
Slideprojector lenses do not have an aperture (not needed when using as loupe), are better to hold and have a bigger diameter than enlarger lenses. So I recommend them over a enlarger lenses. You don't have to go for Leica any brand will be OK. Look for an aperture 2.8 or bigger, those usually were the best versions available and those are also suited best as a magnification loupe because the big diameter makes it easier to look through. In the worst case you have to buy an old slide projector and unsrew the lens .
Edit:
http://www.surplusshed.com/pages/item/l10536.html